Process of extracting copper.



C. H. BBNEDIGT. l PROCESS oP PXTRAGTING COPPER.

APPLOATION FILED APE.1 8, 1914.

jlllg, Patented Mar. i6, MM5.

lsi'. LE'Acl-"NG ZNmLEAcHaNG SoLuTloN. SoLuTloN. IST' WASHL Cu, 0017; WATER Cw 0.57: Cu, 05575 2mg: 0.08% NH, 1,0%L` im, 1.07: l C03 003% 60 0.6% A Cog, 0.8%

a s' Q. s o P H g SAND E31 Q 1 ,q @s N t@ f k 1:0415 zu? .w 0 50 Flm-a NEW NEW Solfursor. Naim/ lsv. LEACHING ZNuLEAcHms f f iS-r Cw 035572' SoLuTioN SOLUTION VH 107 VVA SH J Y D we @am Joobw. A50@ Miam .30o zsm.

DlswrsLLATE. p AWwwnz-a/ &' RECIPI HLM. Em me? I vwm @ls'rmo Cop/verw@ Awww 6P. @,omf 79g ,GW/m7. Smurrfa Y../lwarwmum/ Cw WJ Agonfggggs. C'arona 34:45u@ 7% CENTENNIAL HARRY BENEDICTQOF LAKE'LINDEN, MICHIGAN.

'PROCESS OF EXTRACTING COPPER.

Specification of Letters Patent.

Patented Mar. t6, 1911.5,

Application led April 18, 1914. Serial No. 832,767.

To all whom it may concer/n Be it known that I, CENTENNIAL HARRY BENEDICT, a citizen of the United States, residing at Lake Linden, in the county of Houghton and State of Michigan, have invented certain new and useful Improvements in Processes of Extracting Qopper, of which the following is a specification.

This invention relates to processes of extracting copper from copper-bearing sands or the like by means of dilute ammoniacal solutions of copper, the object of the invention being the provision of a cyclical process which is eiicient and economical in operation, and in Which the losses of ammonia and of copper are minimized.

It has long been recognized that-(1) copi per oXid will dissolve in ammoniacal solutions, yielding copper-ammonium cpmpounds; (2) solutions of cupric-ammonium salts are capable of dissolving native or metallic copper, yielding cuprousammonium salts; (3) these cuprousammonium. salts may be oxidized, by air or otherl suitable oxidizing-agents, to cupric-ammonium salts; and (4) copper-ammonium solutions subjected to distillation, are decomposed with separation of copper oxid, ammonia being volatilized.

It has been attempted to apply ammoniacal solutions to the extraction of copper, including native copper, from its ores, but such processes have not heretofore been commercially successful, owing primarily to the heavy losses of the expensive and hi hly volatile ammonia, and to the high cost o the installation necessary to minimize the losses of ammonia due to volatilization from thel solutions used. The present invention is designed to overcome these and other diiliculties.

My investigations lhave shown that the lossesof ammonia, which have been a very serious factor affecting the commercial success of prior processes, are not due exclusively to volatilization, as has been heretofore assumed, but arise largely from the adsorption of ammonia by the fine sands and slimes, the adsorption by slimes being greater than that by sands. I have also found that the adsorption losses are, in a general Way, proportionate to the concentration of the ammoniacal solution; and that in highly dilute solutions, that is to say solutions containing two per cent. or less of NH3, in the free state or iii unstable combinations with copper, the adsorption losses are so small as not to interfere with the commercial aspects of the process, provided the sands are substantially free from slimes. The use of such highly dilute solutions presents the further advantage of minimizing the losses of ammonia by volatilization. It has not heretofore proven practicable to employ highly dilute solutions of this character for the extraction of copper from sands or other ores, for the reason of such solutions for copper low as compared with that of moniacal solutions, volume of solution and regenerated in quantity of copper is necessarily stronger amwith the result that the which must be handled order to produce a given has been very large, this in turn necessitating a large and costly ini v stallation.

lt is a primary object of the present invention so to operate a cyclical leachingprocess as to render it practicable to use these highly dilute ammoniacal solutions of copper for solvent purposes, securing thereby the advantage of small or negligible losses of ammonia and of copper, Without unduly increasingv the cost and size of the installation. To this end, the cycle of operations is so arranged that an amount of copper equal to that extracted from a given batch of ore will be found concentrated in a relatively small proportion of the total volume of solution brought into contact with this ore. A suitable volume of this stronger solution is subjected to distillation to precipitate its copper-content in the form of oxid, and to recover the free ammonia and any volatile ammonium salts, which are restored to the cycle at the appro riate point, the volume so distilled prefere ly containing an amount of copper practically equal to the total quantity of copper extracted from the ore in the same cycle.

For clearness, the following terminology is used: The terms rich and poor an'd strong and weak are applied to 'the copper-content of the various solutions in the cycle, and the terms high *and low that the solvent capacity are applied to the free ammonia-content of these solutions, all of these terms being of course merely relative.

The present process, in its preferred embodiment, involves an initial leaching-operation with a solution which, in comparison with the solutions following it in the cycle, is richer in copper and preferably lower in free ammonia. A portion of the stronger eiiluent from the ore is subjected to distillation, said portion containing such total quantity of copper that the quantity of dissolved copper in the circuit is maintained practically constant, that is to say, so nearly constant as to allow .a repetition of the cycle: in other words, the quantity of copper recovered by the distillation is practically equal to that entering into solution from the given tion being either water or a substantially barren solution or reject from the distillation. The second leaching-solution, being poorer in copper than the rst solution, is usually somewhat higher infree ammonia;

f and the succeeding solutions, herein for convenience termed washesf are not only poor or nearly free from copper b ut are also,'preferably, successively lower 1n ammonia. The number of successive solutions or washes thus used will depend upon a variety of conditions as hereinafter mentioned.

The following is a typical illustrative A' embodiment. of the process as applied to the treatment of copper-bearing sand in successive batches or bodies of approximately one thousand tons, each batch being treated with four solutions, successively applied. F or simplicity, the process will be described as applied to a single batch of ore, it being of course understood that in the practical "application ofthe invention, it is not essentialto adhere strictly to the precise cycle of operations below described as illustrative of the invention. j

The four typical solutions, as applied to a sand assaying approximately 0.5 per cent.

.of copper, in the order of their application to the sand, are designated and characten ized as follows, percentages being by weight (l) First leaching solution 7: 0.5% Cu: 1.0% NHS: 0.8% CGT Melese (2) Second leaching solution 0.35% Cu: 1.0% NH3: 0.8%'C0,.

(3) First wash: 0.01% Cu: 0.08% NH3: 0.02%. C02.

(4) Second wash: Water, or a distillation reject containing only traces of copper and ammoniacal compounds.

It is of course to be understood that the compositions above given are illustrative only, and subject to some variation in accoi-dance with the copper-content of the' sands, and other circumstances.

rlhe first leaching solution contains ammonia, ammonium carbonate, and cupric-ammonium carbonate from a previous leaching-operation. lThe other solutions, as well as the first leaching solution for subsequent cycles, arise in the course of the process in the manner hereinafter indicated.

A complete representative cycle involved in the treatment of a single batch of copperbearing sands of the character specified is indicated graphically in the accompanying diagram.

Sand finer than forty mesh, previously freed from slime by means of a Dorr classifier or otherwise, is run into a tank which for illustrative purposes may be 54C feet in diameter by 12 feet high. This tank should be covered, fitted with valve-controlled vents, provided with a false bottom of fil ter-cloth supported on a wooden frame and fitted with an overflow and with appropriate means for receiving and delivering the sand and the various solutions. The sand is run in with water in such manner as to be uniformly distributed. After one thousand tons of sand have been delivered to the tank, filling it with sand to a height of about ten feet, the water meanwhile overflowing, theA excess water is removed by decantation and the sand drained, to the surface. rThe first leaching solution is then led into the tank from above, the bottom valve opened, and the water displaced at as rapid a rate as filtration will permit. As soon as ammonia begins to appear at the outfiow, indicating substantial displacement of the water, the lower valve is artially closed and the percolation rate adjusted as may be found necessary to secure a satisfactory solution of the copper-content of the ore. The first por,- tions of the solution are found to be poor in copper and low in ammonia-content, owing to diusion and imperfect displacement, and are run into the sump for the second leaching solution. Soon the first leaching solution, properly enriched in copper and now termed rich solution, appears and is permitted to flow to the ric solution tanks for subsequent distillation. This rich so lution is the richest portion of the euent coming from the sand, and is* ready for distillation. The volume of rich selution distilled for any one batch of sand is dependent y upon the copper-content of the sand,I and `in practice Will be, on the average, such volume that the copper-content of the rich solution distilled is practically equal to the copper extracted from the sand. The rich solution on distillation breaks up into copper oxid for 'the smelter, ammonia and ammonium carbonate for the second leaching solution, and a reject containing traces only ci copper, ammonia andv ammonium carbonate; this reject may be used instead or Water for the second Wash, if desired.

As soon as ,the first leaching solution, amounting in all to some five hundred tons, has .been run upon the sand and has reached the sand line, the second leaching solution is run in, in approximately equal volume;I and when this in turn has all reached the sand line, therst Wash is added, followed in the same manner by the second Wash, the effort in all cases being" to avoid mixing solutions, and to displace each`by that next succeeding it in the cycle. The several efduent solutions are so manipulated as practically to maintain the proper composition balance, as between the chemical contents or the various solutions, a typical method by which this may be done being illustrated graphically in the diagram before referred to. There is thus established an vequililniitn'n in the process, there being also a regular progression of solutions inthe following general manner :-'l`he second Wash oi charge N takes up a little copper and becomes the 'first Wash of charge N+1; this in turn taires up a little more copper and receives the distillate andsome dissolved copper from previous cycles and becomes the second leach' ing solution of charge N-l-Q; the free ammonia of this second leaching solution is partially used in dissolving. copper, when it ecomes the irst leaching solution oi' charge N-j-S, its copper-content having been fully oxidized to the'cupric condition; this rst leaching solution having become saturated with copper by .its passage through the sands, and having thereby lost its solvent power, is in part distilled, 'as before described, depositing its copper values as a 79 per cent. oxid, yielding its ammonia and ammonium carbonate as a pure product to join cycle 'N-l-t as a second leaching solution, andfurnishing from its almost barren reject a second Wash tor a `ollovning cycle. ln a plant containing more than oneleaching-tank, these several operations are oi course all going on at the same time, the total volume of solution in circulation being practically a constant: thus rich solution is continuously 'Withdrawn from the leach- Ving-circuit, and is replaced by an equal vol- 'ume of. second Wash, less only the small volume'o fresh ammonia and ammonium carbonate solution added to replace mee` chanical losses. ln case the distillation is edected by free steam, the' volume of solution is increased by its condensation, and a portion of the reject from the distillation, equal to the steam condensed, is thrown away in the course of each cycle.

The solvent power for native copper of these several solutions is of course dependent upon their content of cupric salts With the required proportion oi" ammonia; and theory indicates that a large amount of oxygen is required to convert the entire copper-content of the solutions to the cupric state. lt has however been shown in practice that it is possible to accomplish this oxidation' through the surface contact of the dilute solutions with the atmosphere, particularly after the process has reached the desired equilibrium, so that relatively large amounts oir' copper are being carried in solution. lt is accordingly unnecessary, as a rule, in they regular operation or" the process, to use any system of mechanical aeration of the several solutions. 'll`hese are stored in covered tanks, with controlled vents, whereby air may be admitted as required. Means for injecting air under pressure may also be fitted both to the storage and leaching tanks. lt has tur-n `ther been shown, in practice, that Whereas there is some appreciable adsorption of ammonia by the sands, even from solutions so dilute as those contemplated under the present invention, the adsorption ci copper is practically m'Z; and the losses of copper are materially reduced by the employment, as described, of at least tvvo leachingsolutions, applied successively, the second leachingsolution being poorer in copper than the first and both solutions being highly dilute.

Obviously, the lo'ss due to ammonia adsorption may be somewhat lessened by repeated washings, and it is possible and may e advisable to have a third Wash5` ifollorving the second Wash, the expediency oie this being a commercial matter, entailing as it Would an additional circuit oi2 pipes, pumps, storage room, and the like. Sio, too, the balance between the amount of rich solution distilled and second Wash used vis in part commercial one, depending upon the costeie steam and the distillation loss, as against the recovery of additional copper and ammonia by more complete Washing.

The present process is to. be distinguished from such processes as depend upon the solvent edect of ammonia, with or Without aeration: in these, the entire copper-content or" the effluent is derived from the ore, and' it is obviously impossible to separate from any fractional por on of this effluent, less than its total volume, a quantity ci? copper equal to that dissolved from the ore. ln other Words, iij a balance is to be maintained in successive cycles, the entire' volume of eiiluent must be subjected to distillation or equivalent treatment for the recovery et wise atsome stage of the process, be submitted to a preci itating operation, in orderthat it may e available for use as a Wash in the succeeding cycles. In contradistinction to these, the present process yields directly from the stronger portions of the effluent a greater or less proportion of barren reject, which is available as a Wash, -or Which may be replaced by a like volume of water available as a Wash: and the volume of liquor tolbe distilled `or otherwise treated for the separation of its copper, is limited to a portion only of the effluent instead of the total volume thereof. If the balance is the initial solution being relatively rich in to be rigidly maintained, the volume thus treated must ofcourse contain an amount of copper equal to the increment derived from the ore; from which it follows that the volume to be distilled is smaller as the leachingsolution, before application to the ore, is

richer 1n copper. The present process, in its"`preferred embodiment, renders it practicable to employ an initial leaching-solution relatively rich in copper, and therebyto reduce the volume of liquid subjected to distillation or equivalent precipitation method, 4to a comparatively small proportion of the total eiluen't: and the use of a second leaching-solution relatively poor in copper avoids the l"necessity, which would otherwise exist,

of using large volumes of Wash Ain order completely to remove the rich solution from the ore. In'other Words, the second leaching-solution, being relatively poor in copper, combines to some extent the functions of a leaching-solution and a Wash; and to the extent that it combines these functions,

reduces the quantity of Wash required.

It will be understood that any person skilled in the art may, with the information derived from the foregoing description, carry out my process with many variations from what I have described in detail as illustrating one embodiment thereof. lEven if lmy described process be not employed in full, there are sundry novel features Which can be utilized to advantage by those skilled in the art. I have endeavored, in the following claims, to point out the various novel features of my invention.

I claim l 1. A cyclical process of extracting copper consists in subjecting a body of the sand to .the successive action of a plurality of solu-v tions, the initial solution containing a cupric-ammonium compound, removing substantially allof the copper from a portion of the stronger eiiiuent, and re-applying the remaining solutions, as solvents, to the treatment of copper-bearing sands.

2. A cyclical process of extracting copper from copper-bearing sands or the like, which consists in subjecting a body of the sand to the successive action of a plurality of solutions, the initial solution containing a cupric-ammonium compound, removing substantially all of the copper from a portion of the efliuent, the amount of copper thus removed being practically equal to the total copper extracted from the sand, and re-applyingl the remaining solutions, as solvents, to the treatment of copper-bearing sands.

3. A cyclical process of extracting copper from copper-bearing sands or the like, which consists in subjecting a body of the sand to the action of a plurality of dilute ammoniacal solutions containing a cupric compound,

copper, removing substantially all of the copper from a portion of the stronger eilluent, and re-applying the remaining solutions, as solvents, to the treatment of copper-bearing sands.

4. A cyclical process of per from copper-bearing sands or the like, which consists in subjecting a body of the sand to the action of a plurality of dilute ammoniacal solutions containing a cupric compound, the initial solution being relatively rich in copper, removing substantially all of the copper fromaportion of the eiliuent, the amount of copper thus removed being practically equal to the total copper extracted from the sand, and re-applying the remaining solutions, as solvents, to the treatment of copper-bearing sands.

5. In a cyclical process of extracting copper, the steps which consist in subjecting thel copper-bearing materialto the solvent action of a plurality of dilute ammoniacal solutions each containing a cupric compound, said solutions of progressively de- A creasing copper-content.

6. A cyclical process of extracting copper from copper-bearing sands or the like, which consists in subjecting a body of the sand to the successive action of a cupricammonium leaching-solution, and a Wash, recovering substantially all of the copper and ammonia from a portion of the stronger effluent, the amount of copper thus removed being practically equal to the total copper extracted from the sand, utilizing the recovered ammonia to re-constitute the leaching-solution, and applying a volume of barren liquid approximately equal to the reject from the copper-recovery process as a Wash in a succeeding cycle.

7. ln a cyclical process of extracting copv ln testimony whereof l @n my signsper from coppey-bearng sands or the ture in presence of tWo Witnesses, like, the steps Whlch consist in subjecting a 'body of the sand to a solution containing a C' HARRY BENEDMM" 5 cuprio ammonium compound, and remov- Witnesses: s

ing substantially all of the copper from a RICHARD H. NICHOLLS,

portion only of the stronger eluent. THOMAS DEARDEN, 

